1. Field of the Invention
The present invention relates to an electric power control device provided in a camera which is constructed in such a manner that a photographing lens, an accessory, and so on can be attached to and detached from a camera body.
2. Description of the Related Art
Conventionally, a camera system has been developed in which a camera body and an accessory including a photographing lens, which can be attached to and detached from the camera body, are arbitrarily assembled. In some camera systems, the photographing lens or the accessory is operated by electric power supplied from the camera body, and the supplied electric power is always monitored in the photographing lens or the accessory, to detect any abnormal state. The monitoring information is transmitted from the photographing lens or the accessory to the camera body. Thus, in the camera body, the check for an abnormal state happens based on the monitoring information. When the abnormal state is recognized, the electric power supply is cut so that a large amount of electric current is prevented from building up.
However, if an electric circuit for monitoring the electric power supply is provided in the photographing lens or the accessory, or if the monitoring information is frequently transmitted between the camera body and the photographing lens or the accessory, not only does the construction of the photographing lens or the accessory become complex, but also the load on the control circuit provided in the photographing lens or the accessory becomes large, and thus, the inherent function of the photographing lens or the accessory maybe lowered. Especially, in the case of a photographing lens, it is preferable that a large load does not act on the control circuit, since prompt lens drive control is required.
Therefore, an object of the present invention is to provide an electric power control device, which can cut the supply electric power without placing a large load on a photographing lens or an accessory when an abnormal state occurs while electric power is being supplied to the photographing lens or the accessory.
According to the present invention, there is provided an electric power control device for a camera having a camera body and a photographing lens which can be attached to and detached from said camera body, the device comprising an electric power source, a monitoring processor, a detecting processor, and a control processor.
The electric power source is provided in the camera body to supply electric power to the photographing lens. The monitoring processor is provided in the camera body to monitor the electric power supplied to the photographing lens and to output a monitor signal in accordance with the electric power. The detecting processor is provided in the camera body to detect whether the electric power is abnormal, based on the monitor signal. The control processor is provided in the camera body to start the supply of electric power from the electric power source to the photographing lens, and stop the electric power supply when the detecting processor detects an abnormal state.
Due to this, when an abnormal state occurs when electric power is supplied from the camera body to the photographing lens, the abnormal state is definitely detected, and since the electric power supply is cut when the abnormal state is detected, electric parts provided in the photographing lens are prevented from being damaged by the excess electric current.
Preferably, the detecting processor comprises a switch that turns ON and OFF in accordance with the monitor signal, and detects the abnormal state based on the ON and OFF state of the switch. The detecting processor may A/D-convert the monitor signal to obtain an A/D-converted value, and compare the A/D-converted value with a predetermined value to detect the abnormal state.
Further, according to the present invention, there is provided an electric power control device for a camera having a camera body and an accessory which can be attached to and detached from said camera body, the device comprising an electric power source, a monitoring processor, a detecting processor, and a control processor.
The electric power source is provided in the camera body to supply electric power to the accessory. The monitoring processor is provided in the camera body to monitor the electric power supplied to the accessory and output a monitor signal in accordance with the electric power. The detecting processor is provided in the camera body to detect whether the electric power is abnormal, based on the monitor signal. The control processor is provided in the camera body to start the supply of electric power from the electric power source to the accessory, and to stop the electric power supply when the detecting processor detects an abnormal state.